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Message-ID: <2375c9f90910200133g51c70ce2x8f90cd79885096a4@mail.gmail.com> Date: Tue, 20 Oct 2009 16:33:40 +0800 From: Américo Wang <xiyou.wangcong@...il.com> To: "Ryan C. Gordon" <icculus@...ulus.org> Cc: linux-kernel@...r.kernel.org Subject: Re: [RFC][PATCH 2/2] binfmt_elf: FatELF support for kernel modules. On Mon, Oct 19, 2009 at 10:41 PM, Ryan C. Gordon <icculus@...ulus.org> wrote: > > Allows kernel modules to be FatELF binaries. > > Details, rationale, tools, and patches for handling FatELF binaries can be > found at http://icculus.org/fatelf/ > > Please note that this requires an updated depmod and modprobe to be truly > effective, but an unmodified insmod can work with FatELF binaries. > > Signed-off-by: Ryan C. Gordon <icculus@...ulus.org> > --- > kernel/module.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++---- > 1 files changed, 67 insertions(+), 5 deletions(-) > > diff --git a/kernel/module.c b/kernel/module.c > index 8b7d880..cda8f79 100644 > --- a/kernel/module.c > +++ b/kernel/module.c > @@ -2066,13 +2066,69 @@ static inline void kmemleak_load_module(struct module *mod, Elf_Ehdr *hdr, > } > #endif > > +/* > + * See if we're a valid FatELF binary, find the right record, and > + * return the offset of that record within the binary. Returns NULL if there's > + * a problem, or a pointer to the real ELF header if we're okay. > + * If we don't see the FatELF magic number, we assume this is a regular ELF > + * binary and let the regular ELF checks handle it. > + * > + * This is a simplified version of examine_fatelf in fs/binfmt_elf.c > + */ > +static Elf_Ehdr *examine_fatelf_module(const unsigned char *hdr, > + const unsigned long len) > +{ > + Elf_Ehdr elf; > + int records, i; > + const fatelf_hdr *fatelf = (const fatelf_hdr *) hdr; As for 'Elf_Ehdr', isn't 'Fatelf_hdr' better? :) > + > + if (likely(le32_to_cpu(fatelf->magic) != FATELF_MAGIC)) { > + return (Elf_Ehdr *) hdr; /* not FatELF; not an error. */ > + } else if (unlikely(le16_to_cpu(fatelf->version) != 1)) { > + return NULL; /* Unrecognized format version. */ > + } > + These braces are unnecessary. > + memset(&elf, 0, sizeof (elf)); > + > + records = (int) fatelf->num_records; /* uint8, no byteswap needed */ > + for (i = 0; i < records; i++) { > + const fatelf_record *record = &fatelf->records[i]; > + > + /* Fill in the data elf_check_arch() might care about. */ > + elf.e_ident[EI_OSABI] = record->osabi; > + elf.e_ident[EI_CLASS] = record->word_size; > + elf.e_ident[EI_DATA] = record->byte_order; > + elf.e_machine = le16_to_cpu(record->machine); > + > + if (likely(!elf_check_arch(&elf))) { > + continue; /* Unsupported CPU architecture. */ This 'continue' can be removed. > + } else { > + const __u64 rec_offset = le64_to_cpu(record->offset); > + const __u64 rec_size = le64_to_cpu(record->size); > + const __u64 end_offset = rec_offset + rec_size; > + const unsigned long uloff = (unsigned long) rec_offset; > + > + if (unlikely(end_offset < rec_offset)) { > + continue; /* overflow (corrupt file?)... */ ditto > + } else if (unlikely(end_offset > len)) { > + continue; /* past EOF. */ ditto > + } > + > + return (Elf_Ehdr *) (hdr + uloff); > + } > + } > + > + return NULL; /* no binaries we could use. */ > +} > + > /* Allocate and load the module: note that size of section 0 is always > zero, and we rely on this for optional sections. */ > static noinline struct module *load_module(void __user *umod, > unsigned long len, > const char __user *uargs) > { > - Elf_Ehdr *hdr; > + Elf_Ehdr *hdr_alloc; /* returned from vmalloc */ > + Elf_Ehdr *hdr; /* adjusted hdr_alloc for FatELF */ > Elf_Shdr *sechdrs; > char *secstrings, *args, *modmagic, *strtab = NULL; > char *staging; > @@ -2094,14 +2150,20 @@ static noinline struct module *load_module(void __user *umod, > > /* Suck in entire file: we'll want most of it. */ > /* vmalloc barfs on "unusual" numbers. Check here */ > - if (len > 64 * 1024 * 1024 || (hdr = vmalloc(len)) == NULL) > + if (len > 64 * 1024 * 1024 || (hdr_alloc = vmalloc(len)) == NULL) > return ERR_PTR(-ENOMEM); > > - if (copy_from_user(hdr, umod, len) != 0) { > + if (copy_from_user(hdr_alloc, umod, len) != 0) { > err = -EFAULT; > goto free_hdr; > } > > + hdr = examine_fatelf_module((unsigned char *) hdr_alloc, len); > + if (hdr == NULL) { > + err = -ENOEXEC; > + goto free_hdr; > + } > + > /* Sanity checks against insmoding binaries or wrong arch, > weird elf version */ > if (memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0 > @@ -2505,7 +2567,7 @@ static noinline struct module *load_module(void __user *umod, > add_notes_attrs(mod, hdr->e_shnum, secstrings, sechdrs); > > /* Get rid of temporary copy */ > - vfree(hdr); > + vfree(hdr_alloc); > > trace_module_load(mod); > > @@ -2538,7 +2600,7 @@ static noinline struct module *load_module(void __user *umod, > kfree(args); > kfree(strmap); > free_hdr: > - vfree(hdr); > + vfree(hdr_alloc); > return ERR_PTR(err); > > truncated: > -- > 1.6.0.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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